Filament support and method of making it



,1 .c. J. SMITHELLS 1,733,976

FILAMENT SUPPORT AND METHOD OF MAKING IT Filed April 25, 1927 Fig. L

Inventor: Colin J. Srnithells,

HIS Attorney.

P tented a. 2 2, 1929 coLm a. SMITEELLS, or BUSI'HEY, ENGLAND, Assreivon. TO GENERAL ELECTRIC com- PANY, A CORPORATION or NEW YORK FILAMENT sufirom' AND MET HOD or MAKING I'll Application filed April 25, 1527, Serial No. 186,488, at! in Great Britain ma 14, 1926. I

It has been found ,that the presence of v chromium or other equivalent metal at a suitable temperature is efl'icient in removing water vapor from an exhausted vessel. This 5 discovery may be applied to the removal of water vapor from thermionic discharge de-' vices, and from incandescent lamps as the removal of water vapor is equally important in incandescent tungsten lamps, especially gas-filled lanips. The object of the present invention is to provide means for maintain- 7 ing such lamps substantially free from water vapor, and to this end chromium is placed in the lamp and maintained at a suitable temperature, preferably by placing the metal on the anchors or wires which support the filament and are raised by conduction of heat from the filament to a temperature exceeding 1000 C. at the part immediately in contact with the filament.

It-has already been proposed to make these anchorsor filament supports of chromium or to plate them with that metal, and thus utilize the power of chromium to Withstand high temperaturesf If this is the object of using chromium, obviously the chromium'must be present on that part of the support; where' the highest temperature is attained, namely that in immediate contact with the filament. On the otherjnand, it is not necessary or even desirable for the purposes of this invention toplace the chromium in this position; for, if the chromium comes into contact with the filament of hot tungsten it is liable to form an alloy with it and thus to injure the filament. "According to the invention the anchors or supporting wires for the filament of -an incandescent tungsten lamp are for most of their length made of chromium or coated with that metal, butthe part of the support immediately in contact with the filament is not composed of or coated with chromium.

The application of this invention to incandescent lamps is illustrated in the accom- 4 panyin drawing in which Fig. 1 isa view of a gaslled incandescent lamp embodying this invention, and Fig. 2 is an enlarged view of a filament support or anchor of this lamp. The lamp shown in'Fig. 1 is a gas-filled lamp having a sealed bulb 1, astem 2, a

glass rod or arbor 3 on the stem, current' lybdenum. Each anchor 6 is supported at 'i one end by the arbor 3, and has at its free end a hook '7 to engage the filament 5; The

bulb 1 contains an inert gas, such as nitro-' .gen or argon.

. In order to maintain the atmosphere in the lamp free from water vapor a mass of chromium 8 is so placed in the lamp as to be heated to a suitable temperature while the lamp is lighted. Preferably, the chromium is so p aced on an anchor .6 as to be heated by conduction from the hook 7 which reaches a high temperature during the operationof the lamp because of its contact with the tungsten filament 5. The chromium may be utilized in the form of a coating or plating on the anchor 6 at a-vpoint close enough to the hook 7 to cause the chromium to become hot enough during the operation of the lamp to remove or render harmless any water vapor that may appear in the lamp. V

One method of'carrying out the invention is to deposit chromium by electrolysis on the filament supportingwires'fi of tungsten or molybdenum. These supports are then mounted in the arbor 3 in the/usualmanner,

but before the filament is wound on the supports the chromium is removed from that part of the support adjacent the hook 7 with which the filament is in contact. A' preferred method of doing this is to direct a small blowpipe flame on' to the hook 7 for a few seconds, whereby the chromium is burnt 01f.

What I claim as new and-desire to secure by Letters Patent of the United States is 1. A filament support for incandescent lamps comprising a wire of refractory meta-,1

shaped at one end to engage a filament, and a coating of chromium over the greater part of(i1ts length but not on said filament engaging en a 2. The method of mal'iing a filament support for electric incandescent lamps which consists in plating with chromium a Wire of refractory metal having one end shaped to hold a filament, and removing the plating from the filament supporting end and adjoining portion of said wire before the filament is wound on the support.

3. The method of making a filament support for electricincandescent lamps which consists in'plating with chromium a wire of refractory metal having one end shaped to hold a filament, and removing the plating from the filament supporting end and ads joining portion of said wire by heating that portion. of the plating with an oxidizing flame before the filament is wound on the support; 1

4. A filament support for a metal filament of an incandescent lamp or similar device comprising a wire of metal with a high melting point and shaped at one end to engagev a filament, and chromium on said wire adjacent to but not on sald filament engaging end.

5. A filament support for a metal filament of an incandescent lamp or similar device comprising a body with a surface of chromium, and a tip of molybdenum Wire in good heat conductive'relation to the chromium surface of said body and shaped to form a filament engaging hook.

6. An incandescent lamp or similar device having a metal filament and a filament support of a wire of metal of high melting point and a body of chromium adjoining said wire and adjacent but out of contact with said filament.

7 An incandescent lamp or similar device having a metal filamentand a filament support wire shaped at one end to engage a filament and chromium'in contact with said wire in position to be out of contact with said fila: ment and to be heated during operation of the lamp by conduction through said wire to a temperature high enough to cause said heated chromium to render harmless any water I vapor present in the lamp.

In witness whereof, I have hereunto set my hand this seventh day of April, 1927.

COLIN J. SMITHELLS. 

